Microwave System

ABSTRACT

A microwave system comprises an antenna, antenna feed, a radio transceiver, and appropriate cabling among the aforementioned. Cost, performance and reliability improvements are achieved with further integration of these elements and with design improvements in the antenna feed. One improvement is the integration of the radio transceiver with the antenna feed. This improvement has many benefits including the elimination of RF cables and connectors. Another improvement is the utilization of the digital cable to power the integrated radio transceiver and a center fed parabolic reflector. One embodiment is disclosed for a radio gateway supporting OSI layers 1-7 supported by an Ethernet cable. Another embodiment is a radio with a client controller suitable for supporting OSI layers 1-3, and supported by a USB cable.

RELATED APPLICATIONS

This application is related to U.S. patent application Patent-TechDocket No. UBNT-01-NPUS00, entitled “Antenna Feed System,” which isfiled concurrently herewith on the same date, and is incorporated hereinby reference.

FIELD OF THE INVENTION

This invention generally relates to wireless communications, and morespecifically, to microwave antennas and microwave radio equipment.

BACKGROUND OF THE INVENTION

The core elements of a microwave system includes a radio transceiver, anantenna, an antenna feed mechanism, and the necessary RF cabling toconnect these elements and one or more client stations. Client stationsare connected to the radio transceiver via digital cables. Theperformance of the microwave system is based upon the characteristics ofthe aforementioned elements and the efficiency of integration of theseelements into a system. There have been many improvement of microwavesystem over the years, and the demand for microwave systems continues togrow, in part due to the large demand for internet service in remoteareas of the world. Thus there is a motivation to have furtherimprovements in the cost and performance of microwave systems.

Some of considerations in an improved cost and performance microwavesystem include:

-   -   Lower cost via a reduced component count and a reduction or        elimination of the expensive RF cable.    -   Higher performance due to reduction of RF cable and RF connector        losses that effect both the transmit power and receive noise        figure.    -   Higher reliability due to a reduced part count and RF        connectors.    -   Improved ease of use when the user set-up only has a digital        interface instead of having both an RF and digital interfaces.    -   Improved ease of use since there are fewer parts required for        the set-up of a radio link.    -   Improved ease of use and functionality when the radio        transceiver and antenna is powered by a digital cable.

Accordingly, the aforementioned factors provide motivation forimprovements in the design of microwave systems.

SUMMARY

The present invention offers significant improvements in theperformance, cost, reliability and ease of use of a microwave system.The core elements of a microwave system include a radio transceiver, anantenna; an antenna feed mechanism, and the necessary RF cabling toconnect these elements. In the present invention, a microwave system isdescribed that comprises a center fed parabolic reflector and a radiotransceiver, wherein the radio transceiver is physically integrated witha center feed parabolic reflector, and wherein the radio transceiver ispowered through a digital cable. Many benefits result from thisintegration, including the elimination of RF cabling and connectors inthe microwave system.

In one embodiment, the radio transceiver has a connector for a Ethernetcable that receives not only the digital signals, but also the power forthe radio transceiver and the center fed reflector. The Ethernet cablecouples to a passive adapter, which in turns couples to a clientstation, wherein the passive adapter is powered by a USB cable that isalso coupled to the client station. The passive adapter injects power inthe portion of the Ethernet cable that couples to the radio transceiver.The length of the Ethernet cable is selected such that there issufficient power to support the radio transceiver and to support thetransmission of the digital signal to the radio transceiver. Thisembodiment may support a radio transceiver that incorporates a radiogateway with OSI layer 1-7 capabilities.

In another embodiment, the radio transceiver has a connector for a USBcable that receives not only the digital signals, but also the power forthe radio transceiver and the center fed parabolic reflector. The USBcable couples to a USB repeater, which in turns couples to a clientstation. The length of the USB cables is selected such that there issufficient power to support the radio transceiver and to support thetransmission of the digital signal to the radio transceiver. Thisembodiment may support a radio transceiver that incorporates a USBclient controller, supporting OSI layer 1-3.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.In the figures, like reference numerals designate corresponding partsthroughout the different views.

FIG. 1 illustrates a prior art design of a microwave system.

FIG. 2 illustrates an exemplary antenna feed system.

FIG. 3 illustrates the antenna feed system in a weather proof housingwith an antenna tube.

FIG. 4 a illustrates the wave pattern of an antenna feed pin on theantenna feed system.

FIG. 4 b illustrates the individual wave pattern of the antenna feedpins and the director pins on the antenna feed system.

FIG. 4 c illustrates the superposition of the antenna feed pins and thedirector pins on the antenna feed system.

FIG. 5 illustrates a microwave system comprising a center feed parabolicreflector incorporating antenna feed system, wherein an Ethernet cableprovides the digital signal and power to the radio transceiver,according to one embodiment of the present invention.

FIG. 6 illustrates a microwave system comprising a center feed parabolicreflector incorporating antenna feed system, wherein a USB cableprovides the digital signal and power to the radio transceiver,according to another embodiment of the present invention.

DETAILED DESCRIPTION

Although described in the context of an IEEE 802.11 Wi-Fi microwavesystem, the systems disclosed herein may be generally applied to anymobile network.

An exemplar embodiment of the present invention is based upon parabolicreflectors, which are well known in the industry. A parabolic reflectoris a parabola-shaped reflective device, used to collect or distributeenergy such as radio waves. The parabolic reflector functions due to thegeometric properties of the paraboloid shape: if the angle of incidenceto the inner surface of the collector equals the angle of reflection,then any incoming ray that is parallel to the axis of the dish will bereflected to a central point, or “focus”. Because man) types of energycan be reflected in this way parabolic reflectors can be used to collectand concentrate energy entering the reflector at a particular angle.Similarly, energy radiating from the “focus” to the dish can betransmitted outward in a beam that is parallel to the axis of the dish.These concepts are well-known by one skilled in the art.

Definitions for this detailed description are as follows:

-   -   Antenna feed—An assembly that comprises the elements of a        antenna feed mechanism, a antenna feed conductor, and a        associated connector.    -   Antenna feed system—A system comprising an antenna feed and a        radio transceiver.

Antenna system—A classical antenna system comprises the antenna feed andan antenna such as parabolic reflector 101. In the present invention, aradio transceiver is integrated with the antenna feed, so the antennasystem comprises an antenna feed system and an antenna.

-   -   Center fed parabolic reflector—a parabolic reflector, and an        antenna feed, wherein the signal to the antenna feed is “feed”        through the center of the parabolic antenna    -   Microwave system—A system comprising an antenna system, a radio        transceiver, and one or more client station devices. The radio        transceiver may be integrated with the antenna system.

FIG. 1 is a diagram of a prior art design 100 of the microwave systemand a client station. The system consists of a parabolic reflector 101,which is supported by a mounting bracket 102. The parabolic reflector101 reflects a RF signal 103 that is emitted from the antenna feedmechanism 104. The antenna feed mechanism 104 receives the RF signal viathe antenna feed conductor 105. As illustrated in FIG. 1, the antennafeed conductor 105 is coupled to an RF connector 106. In turn, the RFconnector 106 is coupled to a coaxial cable or equivalent 107. Thecoaxial cable 107 has a RF connector 106 on each end of the cable.

The other end of the coaxial cable 107 connects to the radio transceiver108, which is located in a weatherproof housing, 109. This weatherproofhousing 109 may be a housing just for the radio transceiver 108, asillustrated in FIG. 1. Alternative, the weather proof housing 109 may bea housing suitable to enclose several electronic devices, includingclient station 114. This latter configuration is not shown.

The radio transceiver 108 converts the RF signal to a baseband signal,based upon the modulation/demodulation algorithms implemented in theradio transceiver 108. For example, the radio transceiver ma implement aIEEE 802.11 transceiver. In this conversion, the baseband signal isencoded in the modulation process and becomes a non-baseband signal.Conversely the non-baseband signal is decoded in the demodulationprocess and becomes a baseband signal. As noted above, the radiotransceiver 108 supports radio frequency (RF) signals, but otherembodiments of the radio transceiver 108 may support other types ofnon-baseband signals such as light or sound.

The radio transceiver 108 has a digital connector 110 that provides theinput/output connectivity for a digital signal. The digital connector110 may be, but is not limited to, an Ethernet connector or a USBconnector.

As illustrated in FIG. 1, for one embodiment, a digital cable 111 is anEthernet cable that connects from the radio transceiver 108 to a powerover Ethernet (POE) device 112. The POE device 112 injects power on thedigital cable 111, such that digital cable 111 supplies power to theradio transceiver 108. The POE 112 receives power from an AC powersource 113. The digital signal is coupled on digital cable 115 from POE112 to a client station 114. The client station 114 may be a clientcomputer such as a laptop.

There are a number of issues to be addressed in an improved performanceand reduced cost microwave system.

First, as illustrated in the prior art microwave system and clientstation of FIG. 1, the RF transceiver 108 is located a distance from theantenna feed conductor 105. As a minimum, a RF cable 107 and four RFconnectors 106 is required. For longer distances a RF bi-directionalamplifier is also required. Thus, there would be considerable benefitsif the radio transceiver 108 was located near the antenna feed mechanism104 or ideally, physically integrated with the antenna feed mechanism104.

Second, a basic antenna feed system has a number of design and selectionconsiderations. In FIG. 1, the antenna feed system includes the antennafeed conductor 105, including an RF connector 106, plus the antenna feedmechanism 104. In the fundamental design, an antenna feed system isplaced with its phase center at the focus of the parabola. Ideally, allof the energy radiated by the antenna feed will be intercepted bad theparabola and reflected in the desired direction. To achieve the maximumgain, this energy would be distributed such that the field distributionover the aperture is uniform. Because the antenna feed is relativelysmall, however, such control over the feed radiation is unattainable inpractice. Some of the energy, actually misses the reflecting area and islost; this is commonly referred to as “spillover”. Also, the field isgenerally not uniform over the aperture, but is tapered, wherein themaximum signal at the center of the reflector, and less signal at theedges. This “taper loss” reduces gain, but the filed taper providesreduced side-lobes levels.

Third, one of the simplest antenna feeds for a microwave system is thedipole. Due to its simplicity the dipole was the first to be used as afeed for reflector antennas. While easy to design and implement, thedipole feed has inherently unequal E and H plane radiation patterns,which do not illuminate the dish effectively and thus reducesefficiency. Another disadvantage of the dipole antenna feed for someapplications is that due to unequal radiation patterns, crosspolarization performance is not optimal. Accordingly, modification to asimple dipole antenna feed is required to achieve 11 optimumperformance, yet cost effective approach.

FIG. 2 illustrates an exemplar antenna feed system 200. As illustrated,the functions of the radio transceiver 108 are integrated with thefunctions of the antenna feed conductor 105, and the functions of theconventional antenna feed mechanism 104. The exemplary antenna feedsystem 200 is located in the same position relative to a reflectiveantenna as the conventional antenna feed mechanism 104. The exemplaryantenna feed so-stem 200 is assembled on a common substrate, which maybe a multi-layer printed circuit board 208, as illustrated in FIG. 2.The antenna feed system 200 comprises a digital connector 201 which isequivalent to digital connector 110 of FIG. 1. This digital connector201 may be an Ethernet or USB connector or other digital connector. Adigital signal from a client station, such as client station 114, iscoupled to the digital connector 201 on a digital cable. To power theradio transceiver in the antenna feed system, the digital cable includesa power component. The power component may be provided on an Ethernetcable, a USB cable, or other equivalent digital cable.

FIG. 3 illustrates antenna element 300 comprising the antenna feedsystem in a housing with an antenna tube 303. The housing may be aweather proof housing as illustrated in FIG. 3 as a plastic housing 301that encloses the elements of the antenna feed system. The antenna feedsystem, its associated housing, and a parabolic reflector is an antennasystem.

As illustrated, the antenna feed system comprises the digital connector201, the printed circuit board 208, the antenna feed pins 205, thedirector pins 206, and the sub-reflector 207. Per FIG. 3, thesub-reflector 207 reflects radiated waves 302 back towards thereflective antenna (not shown). The plastic housing 301 may conform tothe shape of to sub-reflector 207. As an option, the plastic housing 301permits interchangeability of the sub-reflector 207.

The tube 303 may be adjusted to various lengths in order to accommodatereflectors of different sizes. A digital cable, equivalent to digitalcable 111, may be routed through the tube 303 and connected to digitalconnector 201. Digital connector 201 may have a weatherized connector,such as a weatherized Ethernet or USB connector.

Referring back to FIG. 2, the digital connector 201 is coupled to aradio transceiver 203 via conductor 202. Connector 202 may beimplemented by a metal connector on a printed circuit card 208. Theradio transceiver 203 has similar functionality as the radio transceiver108 of FIG. 1. Accordingly, radio transceiver 203 generates an RF signalthat is coupled to an antenna feed conductor 204, which in turn couplesto antenna feed pins 205. The antenna feed pins 205 radiate the RFsignal 103 to an antenna such as parabolic reflector 101. Ho-ever, theradiated signal is modified and enhanced by the director pins 206 andthe sub-reflectors 207. These components will be further discussedherein.

As illustrated in FIG. 2, the antenna feed pins 205 comprise two pinsthat are located on opposite sides of the printed circuit card, and thepins are electrically connected together. FIG. 4 illustrates assembly401 with the radiating patterns 402 from the antenna feed pin 403. Intheir most fundamental structure the antenna feed pin 403 implements ahalf wave length dipole. However, the optimum system design with theinclusion of the director pins 206 and the sub-reflector 207 results ina modified design from that of a half-wave length dipole.

The director pins 206 are known in the industry as passive radiators orparasitic elements. These elements do not have any wired input. Instead,they absorb radio waves that have radiated from another active antennaelement in proximity and re-radiate the radio waves in phase with theactive element so that it augments the total transmitted signal, asillustrated in FIGS. 4 a, 4 b and 4 c. Per FIG. 4 a and element 400,assembly 401 comprises an antenna feed pin 403 that radiates circularwaves 402. Per FIG. 4 b and element 420, these circular waves 402 reachthe proximity of director pins 424 and the director pins 424 generatere-radiated waves 425. The result is that the energy is better focusedtowards the reflective antenna, as illustrated in FIG. 4 c and element440. Per FIG. 4 c, the superposition of the radiated waves 402 from theantenna feed pins 403 and the re-radiated waves 425 from the directorpins 424 result in highly focused waves 446 that are radiated towardsthe parabolic reflector (not shown).

An example of an antenna that uses passive radiators is the Yagi, whichtypically has a reflector behind the driven element, and one or moredirectors in front of the driven element, which act respectively likethe reflector and lenses in a flashlight to create a “beam”. Hence,parasitic elements may be used to alter the radiation parameters ofnearby active elements.

For the present invention The director pins 206 are electricallyisolated in the antenna feed system 200. Alternatively, the directorpins 206 may be grounded. For the exemplary, embodiment, the directorpins 206 comprise two pins that are inserted through the PCB 208 suchthat two pins remain are each side of PCB 208, as illustrated in FIG. 2.In the exemplary, embodiment, the director pins 206 and the antenna feedpins 205 are mounted perpendicular to the printed circuit board 208.Further, these pins may be implemented with surface mounted (SMT) pins.

The perpendicular arrangement of the director pins 206 and the antennafeed pins 205 allows for the transmission of radio waves to be planar tothe antenna feed system 200. In this arrangement, the electric field istangential to the metal of the PCB 208 such that at the metal surface,the electric field is zero. Thus the radiation from the perpendicularpins has a minimal impact upon the other electronic circuitry on PCB208. Hence, approximately equal E and H plane radiation patterns areemitted that provide for effective illumination of the antenna thusincreasing the microwave system efficiency.

The radiation pattern and parameters are additionally modified by thesub-reflector antenna 207 that is located near the antenna feed pins205. As illustrated in FIG. 3, the sub-reflector “reflects” radiationback to a reflective antenna (not shown in FIG. 3.) Otherwise, thisradiation would not be effectively directed. Accordingly, both thedirector pins and the sub-reflector modify the antenna pattern and beamwidth, with the potential of improving the microwave system performance.

The overall performance of the antenna feed system is based upon thedesign of the antenna feed pins 205, the director pins 206, thesub-reflector 207 and the incorporation of the radio transceiver 203 anddigital connector 201. For each of these elements, the location of eachelement in the antenna feed system is determined, and the is dimensionand shape of each element is determined. To optimize the performance,these design considerations are matched with the design characteristicsof the antenna. To facilitate this complex design, a two step designprocess is implemented:

-   -   1. Simulation and analysis using 3D electromagnetic finite        element method (FEM) software. In the industry, this software is        referred to as HFSS, or High Frequency Structure Simulator. HFSS        is the industry-standard software for S-parameter extraction,        Full-Wave SPICE™ model generation and 3D electromagnetic field        simulation of high-frequency and high-speed components. HFSS™        utilizes a 3D full-wave Finite Element Method (FEM) field        solver. HFSS is available from software vendors or may be        developed as custom software.    -   2. Design of the antenna feed system utilizing numerical        optimization software. Genetic algorithms are incorporated in        this software. As a result of this design step, the optimized        physical design is achieved based upon various design        parameters.

Important design parameters include obtaining an acceptable return loss(i.e. maximize the reflected energy) and obtaining high gain (i.e.maximize the focus of the energy). Some other design considerationscould include the radio system standards, including multi-bandconfigurations, antenna configurations, minimizing the form factor,design for easy assembly and manufacturability.

A specific type of parabolic reflector is a grid reflector. A gridreflector offers a small package and light weight design. Hence, theyare useful in rural areas where transportation costs are a key factor.Also, grid reflectors with their small form factor and grid antenna arewell suited for high wind environments.

An alternative to the parabolic reflector is a corner reflector. Acorner reflector is a retro-reflector consisting of three mutuallyperpendicular, intersecting flat surfaces, which reflectselectromagnetic waves back towards the source. The three intersectingsurfaces often have square shapes. Corner reflectors are useful if amodest amount of gain is sufficient, and a smaller form factor and lowercost is desired.

Present Invention

Microwave systems gain significant benefits when they are constructedwith the aforementioned antenna feed system. For example, with theelimination of RF cables, only digital cables are required for theconnection to the center fed parabolic reflector. Thus, installationissues are simplified. Further, there are alternative embodiments thatallow the digital cable to also supply the power to the digitaltransceiver.

One embodiment is microwave system 500 illustrated in FIG. 5. As perFIG. 5, a parabolic reflector 101 is appropriately installed on mountingbracket 102. The parabolic reflector 101 incorporates a center feedassembly as was illustrated in FIG. 3. Antenna element 506 is anembodiment of antenna-element 300. Antenna element 506 also incorporatesan embodiment of antenna feed system 200 (not shown in FIG. 5). Antennaelement 506 comprises a housing and antenna tube as illustrated in FIG.3.

Antenna element 506 comprises an Ethernet connector 510 that is shownseparately for clarity. The digital signal from Antenna element 506 iscoupled via an Ethernet cable 511 to a passive adapter 522, which inturn couples the digital signal to a client station 514 via anotherEthernet cable 511. Additional Ethernet connectors 510 facilitate thecoupling. The passive adapter 522 also comprises a USB connector 520which is coupled by a USB cable 521 to USB connector 520 on the clientstation 514. Via the USB cable 520, power is supplied from the clientstation 514 to the passive adapter 522. In turn, the passive adapter 522injects power into the portion of the Ethernet cable that couples toantenna element 506. Hence, power for antenna element 506, that comprisea radio transceiver and for the parabolic reflector is supplied by theclient station 114.

A typical USB port may supply approximately 500 mw at 5 volts. When thislevel of current is supplied to the passive adapter 622, then there issufficient power to support an Ethernet cable of up to 100 meters inlength. This means that there is sufficient power to “power” the radiotransceiver, and the there is sufficient power to support thetransmission of the digital signal to the radio transceiver. Hence, theparabolic reflector 101 may be located up to 100 meters from the passiveadapter 522.

In the aforementioned embodiment, the radio transceiver may incorporatea radio gateway with OSI laser 1-7 support. Accordingly, full routing,firewall, network translations and network processing capabilities maybe provided. One implementation of the aforementioned radio transceiveris a radio-based Linux RTOS 3 gateway. This functionality is desirableto IT system administrators inasmuch as they may manage the networkwithout distributing the client devices.

An alternative embodiment of the present invention is microwave system600 as illustrated in FIG. 6. Similar to FIG. 5, microwave system 600comprises parabolic reflector 101 with mounting bracket 102, and antennaelement 606. Antenna element 606 is another embodiment of antennaelement 300, as illustrated in FIG. 3. For this embodiment, antennaelement 606 has a digital connector that is a USB connector 520 that isshown separately for clarity. Additionally, the radio transceiver is aradio transceiver with a client controller that supports OS layers 1-3.One implementation is a radio based windows client device.

Similarly to the microwave system 500, the radio transceiver ofmicrowave system 600 is powered by the digital cable. For microwavesystem 600, the USB cable 521 provides the digital signal and power tothe radio transceiver in the antenna element 606. In this embodiment,the USB cable 521 is coupled from the USB connector 520 of the antennaelement 606 to a USB repeater 622. In turn another USB cable 521 iscoupled from the USB repeater 622 to a client station 614. Hence, theclient station 614 provides the power to the radio transceiverincorporated in antenna element 606.

With the aforementioned embodiment, each of the USB cables is limited inlength to approximately 4.5 meters in order to insure sufficient signalperformance and power is received by the radio transceiver. Thislimitation is acceptable in many applications given the significant costreduction with this embodiment.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention. For example, any combination of any of the systems ormethods described in this disclosure is possible.

1. A microwave system comprising: a center fed parabolic reflector. aradio transceiver; and a client station wherein the radio transceiver isphysically integrated with the center fed parabolic reflector, whereinthe radio transceiver receives power through a digital cable, andwherein the digital cable is coupled to the client station.
 2. Thesystem of claim 1 wherein the digital cable is an Ethernet cable.
 3. Thesystem of claim 2 wherein the radio transceiver couples to a passiveadapter via the Ethernet cable, which in turn the passive adaptercouples to a client station via another Ethernet cable, wherein thepassive adapter receives power by a USB cable that is coupled from theclient station; whereas the passive adapter injects power into theEthernet cable that is coupled to the radio transceiver.
 4. The systemof claim 3, wherein the radio transceiver comprises a radio gatewaysupporting OSI layers 1 to
 7. 5. The system of claim 1 wherein thedigital cable is a USB cable.
 6. The system of claim 5 wherein the radiotransceiver couples to a USB repeater via the USB cable, which in turnthe USB repeater couples to a client station via another USB cable,wherein the length of the USB cables is selected such that there issufficient power to support the operation of the radio transceiver 7.The system of claim 6, wherein the radio transceiver comprises a clientcontroller supporting OSI layers 1 to
 3. 8. A method of powdering amicrowave system, the method comprising the steps of: integrating aradio transceiver into a center fed parabolic reflector; coupling adigital cable from a client station to the radio transceiver; andsupplying power from the client station to the radio transceiver overthe digital cable; wherein the digital cable also provides a basebandsignal to the radio transceiver.
 9. The method of claim 8, wherein thedigital cable is an Ethernet cable.
 10. The method of claim 9, whereinthe radio transceiver couples to a passive adapter via the Ethernetcable, which in turn the passive adapter couples to a client station viaanother Ethernet cable, wherein the passive adapter receives power by aUSB cable that is coupled from the client station; whereas the passiveadapter injects power into the Ethernet cable that is coupled to theradio transceiver.
 11. The method of claim 10, wherein the radiotransceiver comprises a radio gateway supporting OSI layers 1 to
 7. 12.The method of claim 1 wherein the digital cable is a USB cable.
 13. Themethod of claim 12 wherein the radio transceiver couples to a USBrepeater via the USB cable, which in turn the USB repeater couples to aclient station via another USB cable, wherein the length of the USBcables is selected such that there is sufficient power to support theoperation of the radio transceiver.
 14. The method of claim 13 whereinthe radio transceiver comprises a client controller, supporting OSI layers 1 to
 3. 15. A microwave system comprising: a center fed parabolicreflector; a radio transceiver; and a client station wherein the radiotransceiver is located between the client station and the center fedparabolic reflector, and is powered over an digital cable coupled to theclient station.